The most successful device for magnetic confinement of high temperature plasmas for thermonuclear fusion research is the tokamak. This uses a toroidal vacuum vessel, into which fusion gases (e.g. deuterium) are injected and heated. Part of the heating is by a large 'toroidal' electrical current (7MA in the Joint European Torus (JET)) which is induced in the plasma and flows around the torus. The magnetic field from this current is referred to as the 'poloidal' field. In addition a toroidal magnetic field is applied by external electromagnets. The operation of the device is based on the reduced energy and particle transport properties of the resultant magnetoplasma.